Magnetic switch



April 13, 1.954 H, REll-EL 2,675,440

7 MAGNETIC SWITCH Filed July 22, 195o 4 F/G.2 y

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I I Hari' Pe/fe/ F/G. 5 BY y v @d 7 Qunzq Patented Apr. 13, 1954 UNITED MAGNETIC SWITCH Harry Reifel, Waltham, Mass., assignor to Stevens-Arnold Inc., South Boston, Mass.

Application July 22, 1950, Serial No. 175,385

(Cl. 20G-90) 4 Claims.

This invention relates to electro-magnetic devices having vibrational, contact closing armatures, such as relays and choppers.

This invention provides an electro-magnetic device such as a chopper, which has the advantages over prior such devices, that its armature does not bounce when it strikes its associated fixed contacts, and that its armature is easily removable and replaceable, and is easily adjustable.

An object of the invention is to reduce the bouncing of a vibrational armature when it strikes an associated contact.

Another object of the invention is to provide for the adjustment of the position of a contact on a vibrational armature.

Another object of the invention is to provide for the easy removal of, and replacement of, a vibrational armature in an electro-magnetic device.

Another object of the invention is to provide for the adjustment, exterior of an electro-magnetic device, of a vibrational armature within the device.

The invention will now be described with reference to the drawing, of which:

Fig. 1' is a side elevation of a chopper embodying this invention;

Fig. 2 is a side elevation, in section, of the chopper;

Fig. 3 is a side elevation of the armature of the chopper;

Fig. 4 is a sectional view along the lines 4 4 ofFig. 2, and

Fig. 5 isa view looking at the left-hand end of Fig. 1 with the end disc removed.

The chopper has a central brass tube I having a circular flange II formed on one end and having the circular flange I2 threaded onto its other end. 'The tube l0 has a central cylindrical opening I3 for the reception of the vibrational armature I4 of magnetizable, spring metal.

The circular insulating disc I is in contact with the outer surface of the flange and extends between same and the aligned inner sides of the brass bar I6 and the ceramic support Il.

The support II' has a central, vertically extending slot in which are placed the contact plates I3 and 2t oi magnetizable metal which are spaced apart by the insulating spacer 2|. The plates I9 and 2c have their outer ends 22 and 23 respectively, extending perpendicular thereto and to which are attached the wires 24 and 25 respectively, for connecting the chopper in a circuit to be controlled.

The circular insulating disc 2%3 is in contact with the outer surfaces of the contact plate ends 22 and 23A and extends between saine and the legs of a permanent magnet 2I which is ii'tted in a recess in the support I1. The circular brass disc 28 having a bent-over upper portion 23 extending perpendicular thereto, is secured to the support I6 by the screws 3G', the support Ii having a flat upper surface 3| on which the disc portion 23 and the outer portions of the bar I5 are seated.

The screws 32 extend through the assembly including the brass disc 28, the support II, the insulating discs 26 and I5, and are threaded into the flange I I, and secure this assembly to the flange.

The bar It has a central portion 33 which is seated upon the upper surface of the upper contact plate I9, and has the screws 33- extending through its outer portions and threaded into the support I'I, the bar thus supporting the contact plates I9 and 20 in position and spaced apart by the insulating spacer 2|.

The cylindrical armature supporting rod 35 which has a diameter slightly less than that of the opening I3 in the tube I3 so that it fits snugly into such opening, is cut away at its inner end to form a at surface to which the outer end of the armature |13 is attached as by spot welding. The outer end of the rod 35 is slotted at 35 for receiving the blade of a screwdriver. The circular ange 3l which has a diameter equal to that of the tube IU., is formed on the rod adjacent its slotted end.

The armature I4 has the spaced apart, contact making, spring strips 3i and 33 of magnetizable metal, with the contacts 39 and IIS respectively, thereon, attached to its inner end as by spot welding, and between its inner and outer ends has the aligned spring strips Iii and E2 attached at their centers, as by spot welding, to the opposite sides of the armatures. The strips 3| and t2 are bowed outwardly between their centers and ends so that they contact the armature only at their centers and ends.

The ange I2 is threaded onto the tube IEE far enough to provide a space between the threaded end of the tube and the outer surface of the 'lange i2 which has a width slig tly less than the thickness of the flange 3l on the armature supporting rod 35. The ange I2 is slitted at one side, and is recessed adjacent the slit for receiving the screw 33 which tightens the ange I2 on the tube I3 for locking it against further rotation. The rod 35 is inserted in the opening i3 in the tube Il) so that the outer, vertical surface ci its flange 31 extends slightly outwardly beyond the flat, vertical, outer surface of the flange I2. The circular brass disc 42 has a central opening through which the outer end of the tube 35 cxtends, and which has a diameter slightly larger than that of the flange I2. It is placed against the outer surface of the flange I2 with the outer end of the rod 35 extending through its central opening, and is secured to the ilange I2 by the screws 43 which are threaded thereinto, and which pull-up thewasher 42 tightly against the flange 31 in the tube for preventing any turning of the armature.

When the armature rod is secured as described in the foregoing, the armature strips 39 and 4i) are positioned between the inner ends of the contact plates I9 and 29 with contacts thereon in alignment with the contacts 39 and 40 on the contact strips. The magnetic field flows through the strips instead of across the gap between the plates I9 and 2li.`

The spring washer 44 is in contact with the inner, vertical surface of the flange I2, and extends between same and the insulating disc 45, the vertical inner surface of which contacts one end of the metal tube 49, the other end of which contacts one vertical side of the insulating disc 41, the other vertical side of which contacts the vertical surface of the ilange II opposite to its vertical surface which contacts the insulating disc I5.

The tube 45 has outwardly turned ends, the inner surfaces of which fit against the outer surfaces of the metal circular plates 42 and against the inner surfaces of which are fitted the outer surfaces of the circular insulating discs 50 and 5I. The coil 52 of insulated wire is wound around the tube 46 between the discs 50 and 5l, and has the ends 53 and 54 for connection to an alternating current source for energizing the chopper as will be described later in this specin* cation.

In assembling the armature within the chopper, the screws 43 are leit sufficiently loose that the armature supporting rod 35 can easily be turned by a screwdriver inserted in its slot 36. An oscilloscope is connected to the wires 24 and 25, and alternating current at the selected operating frequency is applied to the coil 52. The rod 35 is then turned slightly, first one direction, and then another, until the pattern on the oscilloscope shows the desired, uniform make-andbreaks. The screws 43 are then pulled up tightly for locking the armature rod in position.

The spring contact strips 39 and 49 can easily be bent by hand for providing the desired contact spacing.

In operation, alternating current which may be within the range of from 2 to 800 cycles per second in the embodiment of the invention illus trated, is applied through the wire ends t and 54 to the coil 52. This alternating circuit magnetizes the armature I4 so that it has first one and then the opposite polarity. The contact plates I9 and 2U are magnetized by the magnet 21 and each attracts and repels the free end of the armature during alternate half-cycles, causing the device to operate as a single-pole, doublethrow switch. The armature would be connected in the circuit as would be the contact plates I9 and 20, the armature thus being electrically connected, first to one and then to the other of the contact plates as is usual in choppers of this type.

By way of example, the chopper may be used to convert the weak direct currents from a thermocouple into alternating currents for amplication by a vacuum tube amplifier.

The free end of the armature tends to bounce when it strikes the contact plates, and this, if permitted, would result in erratic performance. Such bouncing is effectively damped out by the spring strips 4I and 62. The free ends of the strips touch the armature on the opposite sides thereof and oppose any longitudinal vibration thereof such as would result from bouncing of the armature end.

While one embodiment of the invention has been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated, since modifications thereof may be suggested by those skilled vin the art without departure from the essence of the invention.

What I claim as my invention, is:

1. An electromagnetic device comprising a cylindrical tube, an energizing coil of wirearound said tube, spaced apart contact plates at one end of the tube, an armature supporting rody having a cylindrical portion with a diameter slightly less than the inner diameter of said tube ntted into the other end of said tube, a flexible armature of magnetizable spring metal attached at one end to the inner end of said rodand having its other end between said plates, contacts on said other end ol' said armature between said plates, said cylindrical portion having an outer portionl accessible from the exterior of said device for permitting rotation of said rod for properly positioning said contacts between said plates, Iand locking means at said other end of said tube and accessible from the exterior of said device for securing said rod against movement.

2. A device as claimed in claim 1 in which the rod has a flange in contact with said other end of said tube, and the means for securing the rod against movement includes a member threaded on said other end of said tube, and having an outer portion extending around the flange, and includes a disc around the rod in contact with the flange and attached to said member.

3. A device as claimed in claim 1 in which the contacts are strips of spring metal attached to the opposite sides of the armature, 'and have free ends extending towards the Contact plates.

4. A device as claimed in claim 1 in which the armature has vibration dampening means comprising spring strips secured at their longitudinal centers to the opposite sides of the arma ture, and having free ends contacting the armature and being bowed away from the armature between their centers and ends.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,676,979 Cheeseman July 10, 1928 2,471,594 Weightman May 31, 1949 2,515,077 Clark July 11, 1950 2,547,026 Winkler Apr. 3, 1951 2,571,780 Stoller Oct. 16, 1951 

